3d printed structure

ABSTRACT

A 3D printed structure of an elastic material having at least a first layer and a second layer may be provided. In one implementation, the 3D printed structure may include at least a first wall having a primary structural layer and a first flexible layer, and at least a second wall having a secondary structural layer and a second flexible layer. An axis of the 3D printed structure may intersect the first layer and the second layer and may intersect the primary structural layer and the secondary structural layer. The primary structural layer may have a first rigidity and the first flexible layer may have a second rigidity, the first rigidity being greater than the second rigidity.

TECHNICAL FIELD

A 3D printed structure of an elastic material having at least a firstlayer and a second layer, the 3D printed structure comprising: at leasta first wall comprising at least a primary structural layer and at leasta first flexible layer, at least a second wall comprising at least asecondary structural layer and at least a second flexible layer,

BACKGROUND

A common issue with 3D printed structures is that such kinds ofstructures are often made out of a relatively stiff material, whichmeans that the structure of the 3D printed structure may be relativelyinflexible due to the composition of the material that is used forprinting.

CN 105034361 discloses a honeycomb core containing cells of differentthicknesses and different shapes, and at least part of the wallthickness of the obtained honeycomb unit is gradually increased in thedirection along the center of the honeycomb unit toward both ends of thehoneycomb unit, so that the honeycomb clamp can be added. The contactarea of the core and the panel, and the honeycomb core can be a flat orcurved structure to meet the requirements of the nonlinear curvedstructure, where the honeycomb core has an excellent bending andcompression resistance.

EP 3 213 909 discloses an impact resistant sandwich structurearchitecture for high speed impact resistant structure, comprisingsandwich skins which enclose a sandwich core formed by a plurality ofspacing layers and a plurality of trigger layers, wherein these layersare stacked alternatively in the core.

These types of material are widely used for providing stiffening in theaerospace industry, where these materials are intended to maintain theirshape during application of an external force.

However, in order to attempt to get structures that have acompressibility and flexibility, there have been made numerous attemptsto construct a material that has the desired flexibility while stillmaintaining the structural integrity of the material. Due to theflexibility of the material used for printing, and the weight of thematerial, it may be a difficult task to construct a layered constructionthat has a certain flexibility while still having the desiredcounterforce to maintain its structure in certain areas.

Such flexible layers have often been made using a foam like substance,such as a PU foam, where the foam can maintain a certain form whilestill having a certain flexibility, such as cushions for seats, midsolesfor shoes, padding for luggage, etc. One issue with this kind offlexible layers is that the flexibility of the layers reduces when thestructural strength of the materials is increased, where this alsoincreases the weight of the material. Furthermore, the formation of thiskind of material is often done in large molds, where anyindividualization of the material, such as specialized contouring oftenrequires material to be cut away, and the foam to be sculped aftermanufacturing, as the cost of an individualized mold is too great for itto be a viable option for personal individualization for each user.

Thus, there is a need to for improved structures for individualizationof flexible structures.

GENERAL DESCRIPTION

In accordance with the present description, there is provided a 3Dprinted structure of an elastic material having at least a first layerand a second layer, the 3D printed structure comprising: at least afirst wall configured to deform when a force is applied in a directionof a first axis and configured to return to its original form when theapplied force is released comprising at least a primary structural layerand at least a first flexible layer, at least a second wall configuredto deform when a force is applied in a direction of a first axis andconfigured to return to its original form when the applied force isreleased comprising at least a secondary structural layer and at least asecond flexible layer, where 3D printed structure comprises a thirdaxis, where the third axis intersects the first and the second layer andwhere third axis intersects the primary structural layer and thesecondary structural layer, where the primary structural layer has afirst rigidity and the first flexible layer has a second rigidity, wherethe first rigidity is larger than the second rigidity.

The provision of the above 3D printed structure, where the third axisintersects both layers of the 3D printed structure, and the primary andsecondary structural structure means that the third axis is provided atan angle to first and second layers, where the first and the secondlayers are substantially parallel in relation to each other. This mayalso mean that the angled third axis may extend through the first layer,into the second layer, and continue to a subsequent layer to the secondlayer. Furthermore, the presence of the structural layers in differentwalls of the 3D printed structure, where the first and the second wallsmay have a substantially parallel first axis. This also means that thethird axis is at an angle to the walls of the 3D printed structure. I.e.the third axis may be seen as having an angle that is between the firstaxis which is parallel to the first wall and the second axis which isparallel to the first layer. I.e. if the first axis has an angle that is90 degrees, and the second axis has an angle that is 0 degrees, thethird axis has an angle that may be higher than 0 degrees, but lowerthan 90 degrees, allowing the third axis to intersect at least twolayers of the 3D printed structure, and at least two walls of the 3Dprinted structure.

The intersection of the third axis in layers may mean that the firstlayer and the second layer are different from each other, and that theprimary structural layer and the secondary structural layer areseparated from each other, i.e. where the axis may not intersect thelayers of the first and second structures and/or the structural layersof the walls in the same positions. Thus, the layers of the 3D structureand the structural layers may intersect the third axis in differentpositions of the third axis, i.e. that the intersections in the layersof the 3D structures are at different positions along the third axis,and similarly with the structural layers of the walls.

By positioning the structural layers along the third axis, it may bepossible to obtain a interaction between structural layers and/orflexible layers in different layers of the 3D printed structure, wherethe increased rigidity of the structural layers, compared to theflexible layers, may create a resilience/spring effect between the twolayers, in different walls, allowing different walls of the 3D printedstructure to have a resilient mechanical interaction between the walls,so that the rigidity of the 3D printed structure provided by thestructural layers may follow throughout the 3D printed structure alongthe third axis.

Within the context of the present description, the term rigidity may beunderstood as a rate of flexibility, where the measurement may be madeof a stiffness of a layer, a rate of yield, hardness (i.e. in theunderstanding when a harder layer has a higher rate of rigidity than asofter layer). The rigidity of a certain layer should be understood asthe capability, aptitude or ability of a layer to flex in a certaindirection. An alternative representation of the rigidity, may .e.g. bethe flexibility of the layers, where the primary structural layer (orany subsequent structural layer) may have a first flexibility, and thefirst and/or the second flexible layer (or any subsequent flexiblelayer) may have a second flexibility, where the first flexibility may belower than the second flexibility. The rigidity may be seen as aquantification of the extent of how the layer resists in deformation inresponse to an applied force. The term flexible may be a complementaryconcept to the rigidity, i.e. the more flexible the layer is the lessrigid it is.

Within the context of the present disclosure the term wall may bereplaced with the term wall part, when disclosing a part of the wall.

Within the understanding of the present disclosure the term “layer” maybe understood as a two-dimensional plane of a three-dimensionalstructure. The layer may comprise one or more walls that intersect thetwo-dimensional plane. Within the understanding of the presentdisclosure a “wall” may be understood as a two-dimensional plane of athree-dimensional structure, where the two-dimensional plane may beparallel to the wall and may intersect a plurality of layers of thethree-dimensional structure. Within the understanding of the presentdisclosure a first layer of a wall may abut a second layer of a wall,which may abut a third layer in a wall. Thus, a wall may be seen as astructure having two or more layers stacked on top of each other, orstacked below each other.

The term “structural layer” is intended to differentiate from otherlayers in the wall structure, and where the term “flexible layer” isintended for naming of layers that are not seen as the structural layer,in order to differentiate the structural layer from different layers inthe wall structure, i.e. the flexible layers. The presence of astructural layer and at least one flexible layer in a wall structuredoes not exclude other types of layers in the wall structure, havingdifferent properties than the two layers that are defined as beingstructural and/or flexible layers.

The primary structural layer, the secondary structural layer, thetertiary structural layer or any other structural layer may have a firstrigidity. All the structural layers may have a first rigidity, where thefirst rigidity is higher than the second rigidity. The first flexiblelayer, the second flexible layer, the third flexible layer and/or anyother subsequent flexible layer may have a second flexibility, where thesecond flexibility may be lower than the first flexibility.

In one embodiment, all structural layers in one wall and/or more wallsmay have the same flexibility. In one embodiment all flexible layers inone wall and/or more walls may have the same flexibility.

The provision of a first wall being provided in an elastic material,means that when a force is applied to the wall in a direction of thefirst axis, the wall is capable of absorbing the force, causing the wallto collapse. The force may be seen as being a compressive force, wherethe force up to a predetermined level may cause the first wall tocompress without the wall being deformed away from the first axis. I.e.the wall may maintain its shape up to a certain amount of force.However, when a predetermined threshold of force is a surpassed, i.e.where a force higher than the threshold is applied to the wall, the wallmay deform out of shape, so that one or more layers of the wall maytranslate in a direction that is different from the direction of thefirst axis, i.e. in a direction that may e.g. seen as being orthogonalto the first axis. Thus, the wall may be seen as being bent, or bulgeaway from the first axis, where the force applied to the first wall isabsorbed in the wall structure due to the elasticity of the elasticmaterial, so that when the force is released/removed from the firstwall, the first wall will return to its original shape. I.e. the elasticmaterial will provide a resilient wall structure, where the wall willreturn to its original form after being compressed. Thus, the firstwall, or any subsequent wall may be seen as being resilient. The wallmay be seen as having an uncompressed state, a compressed state, and anintermediate state which may be seen as a state of the wall where acompressive force is applied to the wall, but where the wall has notreached its fully compressive state.

The wall may have a first end which may be seen as the top part of thewall, and a second end, which may be seen as the bottom part of thewall, where the wall is provided with a plurality of layers between thefirst end and the second end. When there is no compressive force appliedto the wall, the wall may have a first length where the first length issubstantially the summation of the height of each layer of the wall.When a compressive force is applied to the wall in a direction that isparallel to the first axis the wall may have a second height, where thesecond height is lower than the summation of the height of each layer.

This means that the wall of the 3D printed structure may have areas inthe direction of the first axis that have higher rigidity than otherareas, that are positioned in other positions along the first axis. Thehigher rigidity allows the primary structural layer, or any otherstructural layer of the first wall, to be less likely to be deformedthan the flexible layer which has a reduced rigidity, compared to thestructural layer. This therefore means that when a compressive force (inthe direction of the first axis) is applied to the wall, where thecompressive force is above a predefined force, the compressive forceapplied to the layers will compress the wall, where the wall will have apredisposition to give in to the compression force, where the wall isallowed to buckle or bend due to the compressive force. Due to thedifference in rigidity of the different layers, the compressive forcewill cause the layer having less rigidity to yield prior to the layerhaving increased rigidity, meaning that the bend and/or buckling of thewall will occur in predefined areas, where the layers having lessrigidity will deflect away from the first axis, before the layers havingthe increased rigidity.

The rigidity and the number of layers may be adjusted in accordance withthe requirements of the 3D printed structure, where the number offlexible layers may be increased for a wall having a lower requirementof force required for allowing the first wall to yield, while anincreased number of structural layers may be applied in order to improvethe resistance to the compressive force. Thus, by the change of theratio of flexible layers vs. structural layers, it is possible to alterthe rigidity of the first wall.

In one exemplary embodiment of the present disclosure the 3D printedstructure may be a 3D printed flexible structure. The 3D printedstructure may be a structure which may be seen as shock absorbing, wherethe 3D printed structure is configured to absorb a force that is appliedto the 3D printed structure. The shock absorption may be provided in theform that the 3D printed structure absorbs an energy of a force appliedto the 3D printed structure, where the 3D printed structure mayelastically deform to absorb the energy. When the force is released theenergy may be released when the elastic deformation is reversed.

The 3D printer structure, and the walls of the 3D printed structure mayhave an original shape, which may be understood as their permanentshape, and a deformed shape, which may be seen as a temporary shape,where the deformed shape may be seen as a shape created by an externalstimulus such as an external force or an external application ofmechanical energy to the 3D printed structure and/or parts of the 3Dprinted structure.

In one embodiment of the present invention the 3D printed structure maybe a 3D printed structure adapted to absorb a force generated by a humanbody. The 3D printed structure may be used as a dampening structurebetween a part of a human body and another entity, i.e. a rigidstructure, such as part of a sole assembly in a shoe, a sitting area ona seat, a pad between a rucksack and the body of a user, a mattress, andsimilar structures that may be used to absorb and distribute energytransferred from a human body to another entity.

Within the understanding of the present invention the term “elasticmaterial” should be understood as a term meaning that the elasticmaterial is capable of stretching, or compressing without plasticdeformation. I.e. where the elastic region of a stress-strain curve islarger than the plastic region of the stress strain curve. I.e. theYoung's modulus of the material may be less than 60 GPa, or preferrablyless than 40 GPa, or less than 20 GPa, or less than 10 GPa.

The term “elastic material” may mean a material that has at least a 50%elongation, or specifically more than 100% elongation, or specificallymore than 200% elongation, or specifically more than 300% elongation.The term percent elongation (elongation %) is a measurement thatcaptures the amount a material will plastically and elastically deformup to fracture. Percent elongation is one way to measure and quantifythe ductility of a material. The material's final length is comparedwith its original length to determine the percent elongation and thematerial's ductility.

The elastic material used for the provision of the layers may be amaterial that has a Shore A hardness of between 30 and 80. The 3Dstructure however, may have a combined lower Shore A hardness than theelastic material, as the material may be made of a number of walls oflayered material that may be separated from each other. Thus, thehardness of the structure may be a combination of the hardness of thewalled structures and the spacing between the walls. Furthermore, due tothe yieldability of the walls, the wall may deflect or bend at ratesthat are lower than at a hardness of the elastic material. Hence, theindividual layers may be stable in the direction of compression force,where the layers compress minimally on an individual basis at the forcewhich they are subjected to.

The order of the structural layer and the first flexible layer and thesecond flexible layer may be the primary structural layer followed bythe first and the second flexible layers, seen in the direction of thefirst axis. The order may also or alternatively be a first flexiblelayer followed by the primary structural layer, which in turn isfollowed by the second flexible layer. The order may also oralternatively be the first flexible layer, followed by the secondflexible layer followed by the primary structural layer.

This means that when a force is applied in a direction parallel to thelongitudinal axis the first and/or second flexible layers will deflectaway from the longitudinal axis before the primary structural layer willdeflect away from the longitudinal axis.

A wall having a structure of layers having identical layers along itsentire length may have a somewhat predictable collapsing force, when acompressive force is applied to the wall in its longitudinal direction,but it may be nearly impossible to predict how the wall will collapse,as the collapse may be the direction of the force, when the force is notcompletely parallel to the longitudinal axis, that has a huge impact onhow the wall may collapse or bend. Furthermore, another issue is thatwhen the wall collapses, it may lose most of or all of its counterforceto the compressive force, so that the wall loses most of its opposingforce as soon as it collapses, as it may fold and/or collapsecompletely.

However, by applying a structure of structural layers and flexiblelayers, that may e.g. be in a repeating structure along the longitudinalaxis it is possible to predict where the first wall will give in to thecompressive force, as the flexible layer may have a reduced stiffnessand/or resistance to the force, so that the wall will in all likelihooddeflect in the areas having the flexible layers, before it will deflectin the areas having the structural layers. Thus, it may be possible tohave the wall collapse/deflect to the compressive force in a predictableway, which makes it easier to configure the wall to collapse at acertain force. Furthermore, this allows the wall to collapse or deflectin a controlled manner, so that the counterforce to the compressiveforce may be maintained by the structural parts of the wall, even thoughthe flexible parts have deflected or have collapsed between thestructural parts.

The first wall may be a part of a larger structure, where each layer ofthe wall may correspond to a layer of a larger 3D structure, and wherethe larger 3D structure may have a plurality of layers. The first wallmay be part of a structure having a second wall, a third wall, orsubsequent walls. The first wall may be part of a structure, where thefirst wall is a part of a cellular structure, where the first wall ispart of a closed cell (seen from above), such as a circular, annular,triangular, hexagonal, or any suitable polygonal closed cell, where thefirst wall and/or a plurality of walls define the volume of a cell.

In one or more embodiments where the 3D printed structure may comprise athird layer and optionally further comprises at least a third wallcomprising at least a tertiary structural layer and at least a thirdflexible layer, where the third axis intersects the third layer and thetertiary structural layer. Thus, the 3D printed structure may beprovided with a further wall having a tertiary structural layer, as wellas at least a third layer of the 3D printed structure, where the thirdaxis both intersects the third layer, as well as the third structurallayer. Thus, the third wall may provide a further connection to thefirst and the second wall in order to provide a resilient relationshipbetween the first and second wall, as well as the third wall. As thethird axis intersects the tertiary structural layer, the increasedrigidity of the three structural layers, compared to the flexible layerswhich may surround the structural layers in the walls, may follow thethird axis through multiple layers and multiple walls of the 3D printedstructure.

In one or more embodiments the first wall, second wall, and/or thirdwall may comprise a primary first axis, secondary first axis and atertiary first axis, respectively. The first second and/or third wallsmay each comprise a first axis, where the structure of the flexible andstructural layers in the wall may follow the first axis. The structuremay differ from one wall to the other, or it may be similar for eachwall, e.g. where the positioning may be shifted from one wall to theother. I.e. where the structural layer is in the first layer in thefirst wall, in the second layer in the second wall, and in the thirdlayer in the third wall, and so on.

In one or more embodiments the primary structural layer and thesecondary structural layer may be positioned in different layers in the3D printed structure. By providing the primary structural layer and thesecondary structural layers in different layers of the 3D printedstructure it may be possible to shift the rigidity of the wall in adiagonal manner from one wall to the other wall, i.e. where theincreased rigidity in the second wall is provided in a layer that islower or higher than the structural layer in the first wall.

In one or more embodiments the tertiary structural layer may bepositioned in different layers in the 3D printed structure than theprimary and/or secondary structural layers in the 3D printed structure.Thus, the tertiary structural layer may be in a layer that is differentfrom the primary and secondary structural layers. I.e. if the primarylayer is in the first layer, the secondary in the second layer, thetertiary structural layer may be in a layer that is different from thefirst and/or the second layer. Thus, the structural layer may thereby beshifted in height from one wall to the other, allowing the rigidity ofthe structural layer to be translated along the third axis.

In one or more embodiments the first wall may abut the second wall,and/or where the third wall may abut the second wall. By having thefirst and the second wall abutting each other, and optionally having thethird wall abutting the second wall, it may be possible to translate therigidity from one wall to the other directly. Thus, the rigidity of thestructural layer in one wall may be transferred directly to another wallwhere the rigidity of the wall will be influenced by the structurallayer in the abutting wall. Furthermore, by having the walls adjacent toeach other, and having a third axis which intersects the structurallayers, the rigidity may translate from one wall to the other, andcreate a cooperative effect that translates between the walls of the 3Dprinted structure.

In one or more embodiments the first wall and the second wall, andoptionally the third wall may form part of a closed cell defining apredefined volume of the cell. Thus, the closed cell seen from above mayhave a view where the walls define a boundary for the cell, and may beparts of a plurality of walls that create the closed cell. The closedcell, may e.g. have six walls, that are connected in an annular manner,e.g. as a hexagonal shape, where the first wall abuts the second walland the third wall abuts the second wall, and the fourth wall abuts thethird wall, etc. The closing of the cell may e.g. be where a sixth wallabuts the first wall, on the opposite side of the first wall. By havinga structural layer in each wall, and the layers may be intersected by athird axis, the structural layers may translate in an upwards ordownwards direction when comparing one wall to its abutting wall. Thus,the rigidity of the walls of the closed cell may alter from one wall tothe other. The closed cell may have any suitable form.

In one or more embodiments the third axis may be a helical axis and/or aspiral axis. By providing the third axis in the form of a helical and/orspiral axis the axis may follow a coiled path, where the coiled path maye.g. follow the walls (i.e. the peripheral walls) of a closed cell. Byproviding the third axis in e.g. a helical path, and where the thirdaxis intersects a structural layer in a wall, the structural layers ofthe walls may also follow a helical path. This therefore means that therigidity of the walls may be formed in a helical manner, so that aclosed cell may e.g. have a rigidity profile which emulates a coiledspring along the periphery of the closed cell. This therefore means thatthe walls of the closed cell may perform in a similar manner to a coiledspring, where a force applied in a direction of a first axis istransferred from one wall to the other via the structural layers, wherethe force is transferred both in a sideward direction (second axis) aswell as a upwards and/or downwards direction when following the path ofthe helical axis. Thus, the walls and the structural layers may beutilized as a mechanical device which may be used to store energy andsubsequently release it to absorb shock or to maintain a force betweencontacting surfaces.

In one or more embodiments the primary structural layer is part of thefirst layer and the secondary structural layer may be part of the secondlayer. Optionally, the tertiary structural layer may be part of thethird layer. This provides a structure of the walls, where thestructural layers of walls may be offset one layer compared to theprevious wall. This may also mean that where the structural layer ispositioned in a layer, the structural layer is an integral part of thelayer, or the layer in a certain position may comprise or consist thecorresponding structural layer.

In one or more embodiments intersection of the third axis in the primarystructural layer may be in the same position as in the intersection inthe first layer and the intersection of the third axis in the secondarystructural layer may be in the same position as the intersection of thesecond layer. Optionally, the intersection of the third axis in thetertiary structural layer may be in the same position as theintersection of the third layer. Thus, the third axis will intersect thestructural layer and the layer in the same position, so that theintersection in one layer and one structural layer may be seen in atleast one point in a three-dimensional space.

In one or more embodiments the primary structural layer and/or the firstand/or the second flexible layers may be attached to another layer via aboundary, where the boundary between the two layers may have a rigiditythat is less than the rigidity of the primary structural layer and/orthe flexible layer. This means that when the first wall deflects fromthe first axis, the deflection of the two layers may pivot across theboundary (seen in a cross-sectional view). This means that the layersmay deflect in a predefined area, which means that the deflection of thefirst wall may be predicted and/or anticipated, which may assist incontrolling the deflection by adjusting the rigidity of the layers, orthe rigidity of the boundary between the layers.

In one or more embodiments the structural layer may have a first surfaceand a second surface. The first surface and/or the second surface of thestructural layer may be seen as the part of the layer which intersectswith the first axis, when the first wall is in an uncompressed state.The first surface and/or the second surface of the structural wall maybe seen as the part of the layer which faces a preceding or subsequentlayer of the first wall. Thus, the first surface and/or the secondsurface may have a tangential axis (seen in a cross-sectional view) thatis substantially orthogonal to the first axis. The first surface and/orthe second surface may be seen as the part of the layer that abutsanother layer of the wall.

The uncompressed state of the first wall may be where the first axisintersects all the layers of the first wall and/or at least a pluralityof the layers of the wall, when the wall is constructed in a linearmanner, where each layer of the wall is stacked on top of each otheralong the first axis. The intermediate state of the first wall may e.g.be where the first axis intersects all the layers of the first walland/or at least a plurality of the layers, where the compressive forcemay e.g. be too low to force one or more layers of the wall to deflectfrom the first axis. The compressed state of the first wall may be whereat least one layer of the first wall is deflected away from the firstaxis.

In one exemplary embodiment the primary structural layer may abut thefirst flexible layer and the second flexible layer along the first axis.This means that the primary structural layer of a first wall may have afirst flexible layer on a first side of the primary structural layer,and a second flexible layer on an opposite second side of the primarystructural layer. Thus, the first axis may intersect a flexible layer, astructural layer and a flexible layer in this order along the length ofthe first axis. This allows the primary structural layer to besurrounded by flexible layers, i.e. on top and bottom, allowing theflexible layers to deform prior to the deformation of the structurallayer when a force is applied to the first wall.

The structural layer may be any kind of structure that creates a wallhaving an increased rigidity compared to the flexible layers. Thestructural layer may comprise a plurality of layers in the direction ofthe first axis, where the layers may be stacked on top of each other,creating a part of a wall having an increased rigidity. The structurallayer may have a height in the direction of the first axis that issimilar or the same as the height of a first layer. However, thestructural layer may alternatively have a height that is larger than theheight of the flexible layer.

In one or more embodiments the first layer may abut the second layer ina direction of a first axis. This means that the first layer may bepositioned on top of the second layer, or may be positioned below thesecond layer. By positioning the layers on top of each other the firstlayer and the second layer provide a part of the 3D printedconstruction, which may be constructed as a structure of multiple layersthat may be positioned on top of each other. The wall parts of the 3Dconstruction may therefore create a 3D printed structure where one layerof a wall structure may have a different rigidity than another layer ofthe same wall structure, and/or where one layer of a wall part may havea different rigidity than a layer of a different wall part in the samelayer

In one or more embodiments the second wall part of the second layer maycomprise a secondary structural layer or a third flexible layer Byproviding the second wall part with a secondary structural layer or athird flexible layer, the 3D printed structure of the first wall partmay have as many layers as the second wall part, and may have a similarrigidity or a lower rigidity than the first wall part, respectively.I.e. when both the first wall part and the second wall part have thesame number of layers, and where both wall parts have a structural layerand a flexible layer, their combined rigidity is substantially similar.However, when the first wall part and the second wall parts do not havethe same amount of flexible and structural layers, the rigidity of thewall part having fewer structural layers is lower than the wall parthaving a higher number of structural layers. Thus, it is possible tocontrol the rigidity of the wall parts by adjusting the number ofstructural and flexible layers.

In one or more embodiments the first flexible layer may abut thesecondary structural layer or the third flexible layer. This means thatthe secondary structural layer or the third flexible layer may provide aspecific structure to the second wall part, where the secondarystructural layer may increase the combined rigidity of the second wallpart by abutting the second flexible layer, or the third flexible layermay ensure that the rigidity of the second wall part is lower than thecorresponding layers of the first wall part.

In one or more embodiments the 3D printed structure may comprise a thirdwall. The third wall may provide the 3D printed structure with anincreased variability, where the third wall may be constructed ofsimilar layers as the first wall and/or the second wall, but where thethird part may have a different layered structure in the direction ofthe first axis than the first and/or the second wall in thecorresponding layers. Alternatively, the third wall may have a similarstructure to the first wall and/or the second wall, should this berequired by the construction of the 3D printed structure.

In one or more embodiments the first layer may further comprises a thirdwall part, where the third wall part comprises in the first layer asecond flexible layer or a secondary structural layer. The third wallpart may provide a further layer to the 3D printed structure, where thethird wall part may have a similar rigidity as the first wall partand/or the second wall part in the same layer, or may have a differentrigidity, i.e. higher or lower rigidity, than the first wall part/and orthe second wall part.

In one or more embodiments the second layer comprises a third wall part,where the third wall part comprises a flexible layer or a structurallayer in the second layer. The third wall part may have the same numberof layers as the first wall part and/or the second wall part, so thatthe height of the first, second and third wall parts is same.

In one or more exemplary embodiments the first wall, the second wall,third wall or any subsequent wall may have a first height and a firstend and a second end, where a primary structural layer is positioned atleast a distance of 20% of the first length from the first end and/or atleast a distance of 20% from the second end. The first height may be thedistance from the first end to the second end along a first axis. Thus,in one example where the first wall has a height of 10 mm, a primarystructural layer may be positioned in an area that is between 2 and 8 mmof the height of the first wall. This means that the wall may have astructural layer that is positioned in a central region of the wall.Therefore, a central area of the first wall may have both a first andsecond flexible layers as well as a structural layer. Thus, it may bepossible to control the deformation of the first wall when a force isapplied to the wall. In a second example the central region of the firstwall may have two or more structural layers, where the structural layersmay be separated by one or more flexible layers.

In one or more embodiments the first wall may abut the second walland/or the third wall may abut the second wall, in a direction along asecond axis. This means that the walls may extend in a certaindirection. The second axis may also be part of a circular direction,where the first wall, second wall and third wall may be connected in anannular or polygonal manner, creating parts of a closed structure, suchas a cell. Thus, the first, second and/or third walls may abut eachother in an annular manner, or parts of an annular manner, where thewalls form a part of an annular structure.

In one or more embodiments the second flexible layer may abut the firststructural layer. The second flexible layer may abut the firststructural layer in a direction along a second axis, where the secondflexible layer is positioned to the side of the first structural layerseen along the direction of the second axis.

In one or more embodiments the flexible layer may have a primary surfaceand a secondary surface. The primary surface and/or the secondarysurface of the flexible layer may be seen as the part of the layer whichintersects with the first axis, when the first wall is in anuncompressed state. The primary surface and/or the secondary surface ofthe flexible wall may be seen as the part of the layer which faces apreceding or subsequent layer of the first wall. Thus, the primarysurface and/or the secondary surface may have a tangential axis (seen ina cross-sectional view) that is substantially orthogonal to the firstaxis. The first surface and/or the second surface may be seen as thepart of the layer that abuts another layer of the wall.

The layers of the first wall may fuse, bond, blend, integrate and/ormerge where the boundary between two layers of the wall may beindistinguishable when the wall structure has been formed. However,during the 3D printing of the first wall or any subsequent wall, thewall is formed layer by layer, where one layer is positioned on top of apreceding layer (a layer that has already been formed and positioned)where a first surface of the preceding layer abuts a second surface ofthe subsequent layer (a layer that is positioned on top of the precedinglayer). The positioning of the two layers may occur prior to curing, sothat the first and the second surfaces intersect, and may be indistinctfrom each other. Alternatively, the first surface may bond or adhere tothe second surface in a permanent manner, where the boundary between thetwo layers may be seen in microscopic view of a section of the firstwall or any subsequent wall.

In one or more embodiments the rigidity may be in the longitudinaldirection. The longitudinal direction may be a direction that isparallel to the first axis of the first wall. The rigidity of the layersof the first wall or any subsequent wall may be seen as a rigidity whichrepresents the flexibility of the layer in the longitudinal direction.I.e. where the rigidity represents how the layer is predisposed ofmoving in a longitudinal direction. A high rigidity will mean that thelayer may need an increased force to dispose the layer in a longitudinaldirection, compared to a layer having a lower rigidity, and vice versa.

In one or more embodiments the rigidity may be in a transversedirection. The transverse direction may be a direction that istransverse to the first axis of the first wall. The rigidity of thelayers of the first wall or any subsequent wall may be seen as arigidity which represents the flexibility of the layer in thetransversal direction. I.e. where the rigidity represents how the layeris predisposed of moving in a transverse direction. A high rigidity willmean that the layer may need an increased force to dispose the layer ina transversal direction, compared to a layer having a lower rigidity,and vice versa.

In one or more embodiments the rigidity may be in a rotationaldirection. The rotational direction may be a direction that rotatesalong a longitudinal axis of a layer first wall, where the longitudinalaxis of a layer of the first wall may be substantially orthogonal (rightangled) to the to the first axis of the first wall. Thus, the rigidityof the layers of the first wall or any subsequent wall may be seen as arigidity which represents the flexibility of the layer in a rotationaldirection. Thus, when a compressive force is applied to the wall of thestructure, the one or more layers may deflect away from the first axisof the wall, where a layer may be bonded to another layer, which meansthat the compression force will cause a torque to be applied to thelayer or both layers. The rigidity of the layer may in a rotationaldirection may e.g. represent the connection between two layers, therotational flexibility of a single layer. The flexibility in arotational direction may be seen as the resistance to a twisting motionof the layer in response to an applied force, i.e. how the layer resistsa rotational motion in response to an applied force. The rotationalrigidity and/or stiffness may also be seen as the torsional rigidity,stiffness and/or flexibility.

In one or more embodiments the structural layer may have a width(transversal to the longitudinal axis) that is larger than of thethickness of the flexible layer.

The structural layer has a width (transversal to the longitudinal axis)that is more than 110%, 120%, 130%, or 150% of the thickness of theflexible layer. The structural layer may have a width that is aboutdouble the width of the flexible layer.

The structural layer may be formed as two or more layers of flexiblematerial that abut each other in a transversal direction. This meansthat the two layers may be positioned in a single layer of the walledstructure, and where each layer bonds to the preceding and/or subsequentlayer of the structure as well as the layer beside in a transversedirection. Thus, the primary structural layer, or any subsequent layermay be constructed of two or more layers of material, where each layeris comparable to the flexible layer of the walled structure. Theprovision of two or more layers of material to form a structural layerwill increase the rigidity of the layer of the wall, as the material mayhave an increased width, when the two or more layers are bonded to eachother, as well as being bonded to the abutting layers in thelongitudinal direction. The two abutting layers may have a height (inthe longitudinal direction) that is comparable or the same as the heightof the flexible layer, where the introduction of the abutting layer doesnot alter the height of the structural layer. Thus, the structural layermay have a similar or the same height as the flexible layer.

In one or more embodiments the first wall may have at a secondarystructural layer and/or at least a third flexible layer. The secondarystructural layer may be further provided to a wall of the 3D printedstructure, in continuation of the primary structural layer and/or aflexible layer, where the further structural layer may be provided toincrease the height of the wall and/or to increase the rigidity of thewall. A third flexible layer may further be provided to the wall of the3D printed structure in continuation of the primary structural layer,secondary structural layer, first flexible layer and/or the secondflexible layer, where the further flexible layer may be provided toincrease the height of the wall and/or to decrease the rigidity of thewall. The first wall or any subsequent wall may be provided with aplurality of structural and/or flexible layers in order to provide apredefined length of the wall along the direction of the first axis.

In one or more embodiments the order of the structural layer and theflexible layers may be repeated along the first axis. This means thatthe order of the structural and the first and the second flexible layersmay be reproduced along the length (along the first axis) the wall,where the primary structural layer and the secondary structural layersmay be separated by one or more flexible layers, in one example, the twostructural layers are separated by two flexible layers. Thus, the lengthof the wall may have a structure where a structural layer may abut oneor two flexible layers on each side (above and below along thelongitudinal length) where this order may be repeating along the lengthof the wall.

In one or more embodiments the first wall may have a repeating layeredstructure along the longitudinal axis of at least one primary structurallayer and at least one flexible layer.

This means that the flexible layers may be configured to defer from thecompressive force which is applied to the first wall, in the areas thatare between two structural layers, so that the wall can reduce in heightfrom its first end to its second end.

In one or more embodiments the primary and the secondary structurallayers may be separated by at least the first flexible layer. Byseparating the primary and the secondary structural layer with at leastone flexible layer, it is possible to control the deformation of thefirst wall along its longitudinal axis, where the flexible layer, whichhas a lower rigidity than the structural layer will deform prior to thedeformation of the structural layers. Thus, it is possible to predictmore precisely on how the first wall deforms, and it is thereforepossible to adjust the rigidity of the structural layer, and/or anywalls surrounding the first wall, to provide a first wall having apredictable and controllable collective rigidity of the entire wall onits own.

In one or more embodiments the height of the structural layer may besubstantially similar to the height of the flexible layer. By providingthe structural layer in a similar height as the flexible layer, where inone or more embodiments the height of the structural layer is the sameas the flexible layer, it may be possible to exchange a structural layerwith a flexible layer, and vice versa, during the construction of thewall, without having to recalibrate the total height of the wall due tothe exchanging of one structural layer with a flexible layer, or viceversa. Thus, the length in the direction of the first axis (height ortotal height) of the wall to be manufactured/printed may be defined outof the total number of layers, where the specific number of the specificlayers does not influence the length of the wall, and the specific typeof layer can be interchanged without specific modification andcalculation of the total length of the wall. This also means that theintroduction of a structural wall can be done selectively in anyposition in a layer of the article to be 3D printed, without influencingsubsequent layers of article, and there is no need to compensate for thestructural layer in a subsequent layer of the wall.

In one or more embodiments the primary structural layer may be separatedin the longitudinal direction by two or more flexible layers. Byseparating the primary structural layer with two or more flexiblelayers, it means that in the longitudinal direction (direction of thefirst axis) the primary structural layer is followed by at least twoflexible layers. This means that the at least two flexible layersprovide the wall with a zone (in the longitudinal direction) that may beseen as more flexible (less rigid) allowing the wall to collapse in thiszone in an easier manner. Thus, the provision of two flexible layersabutting each other in the direction of the first axis, may also meanthat the flexibility of the bond between the two layers is less thanbetween a structural layer and a flexible layer, which may mean that oneflexible layer may deflect easier from the other flexible layer, when acompressive force is applied to the wall in the direction of the firstaxis.

In one or more embodiments the first flexible layer may abut the primarystructural layer. By having a primary structural layer abut a firstflexible layer, in the direction of the first axis, the flexibility ofthe wall may be increased in the direction of the first axis. Theflexible layer will have a lower rigidity that the structural layer, sothat the total rigidity of the two layers combined will be less thanhaving e.g. two structural layers abutting each other. Thus, it ispossible to increase the flexibility of the wall by a provision of aflexible wall, without changing the composition of the material used for3D printing.

In one or more embodiments the first axis may intersect a central axisof the structural layer and/or the flexible layer. This means that thefirst wall may be provided in such a way that the structural andflexible layers are provided in a linear manner, where each layer isstacked on top of each other in a direct manner, so that any compressionforce that is applied to the first wall in a direction parallel to thefirst axis, is transmitted through all the layers of the wall that havea central axis that intersects the first axis. The central axis of thelayers may be seen as a longitudinal axis that follows the length of thelayer, and may be seen as perpendicular to a cross sectional plane ofthe layer.

In one or more embodiments the elastic material may be a siliconematerial or a mixture of a silicone material. The 3D printing may bedone by adding one layer on top of another layer, and continuing thisuntil the wall has a desired height. The 3D printing may advantageouslybe done using a liquid form polymer, that cures when it has beenpositioned in its correct position. Thus, the 3D printed structure maybe made of a polymeric material when cured. An example of this is aliquid silicone polymer, that is added in in the same direction as thelayer which it is positioned on top of, so that a wall may be a numberof discrete lines of polymer added on top of each other, where the linesare parallel to each other when 3D printed on top of each other. Thematerial is advantageously elastic, so that the deformation of thematerial, during application of pressure is reversible, and the materialdoes not plastically deform when it is elastically deformed, I.e. havinga high ratio of stress/strain relationship before a plastic deformationoccurs.

In one embodiment the hardness of the polymer may be between 20 and 90Shore A when cured, preferably between 30 and 85 Shore A, morepreferably between 35 and 80 Shore A, more preferably around 40 to 60Shore A. One example of a polymer is silicone, where one type may be DowCorning LC3335 Liquid Silicone Rubber designed for 3D printing, havingapproximately 50 Shore A hardness. Other types of polymers and siliconesthat are adapted for 3D printing may also be utilized, and the specifictype of silicone or polymer is not essential for the invention, but theelasticity, the hardness and the capability of 3D printing may be seenas the important factor.

The 3D printing method use is the Fusion Deposition Modelling, thatforces two defined fluids through a static mixer, which subsequentlyextrudes out of a nozzle, which depends on the precise application. Oneprinting apparatus that may be used is the German RapRap GMbH 3D printerX400 PRO 3D printer. Other types of printers could be used.

In one embodiment the thickness of the each layer may be between 0.1 and1.6 mm, more preferably between 0.2 and 1.2 mm, more preferably between0.3 and 1.0 mm, or more preferably between 0.4 and 0.9 mm. The thicknessof the layers may be controlled by either the thickness of the 3Dprinted lines, and/or a multiplicity of the 3D printed lines. Thethickness of the lines may control the resistance of the walls, as anincreased thickness will provide an increased resistance and/orincreased rigidity.

In one or more embodiments the structural layer may be made from a firstmaterial composition and/or where the flexible layer is made from asecond material composition, where the first material composition isdifferent from the second material composition. Thus, the 3D printedstructure may be made out of at least two different materialcompositions, where the material composition may influence the behaviourand the compressibility of the layers when applied with a compressiveforce.

The form of the 3D printed structure may be adjusted by providing thewalls in a different number of layers, where the part of the 3D printedstructure that is intended to have a reduced height may be provided withwalls having a low number of layers, where the parts of the 3D printedstructure that is intended to have an increased height may be providedwith an increased amount of layers positioned on top of each other.

In an example where the 3D printed structure may be a midsole for ashoe, the areas that are intended to have a lower height may e.g. be theforefoot area, where the higher areas may e.g. be the arch area on themedial part of the 3D printed structure, and e.g. the heel area. Thus,as the 3D printed structure may be utilized to be formed completelyafter the form of the foot of the specific user, the shoe which themidsole is to be used in may be formed in a relatively generic form,where the upper and the outsole may be joined together, where innersurface of the outsole may be relatively flat and not shaped to the formof the foot in the sense of the height. Thus, the inner surface of theoutsole, i.e. the foot facing surface of the outsole, or the foot facingsurface of the shoe, if it is provide with an intermediate part, may berelatively flat, and may be provided as a receiving surface for thelower part of the 3D printed midsole. Thus, the foot facing surface ofthe outsole may be provided in the shape of the foot, in thelongitudinal and transversal directions but not having anycharacteristic foot shape in the height direction, i.e. in the directionperpendicular to the longitudinal and/or the transversal direction ofthe foot. Thus, a shoe having the correct size (along the longitudinalaxis of the shoe) for the user, may be provided with a 3D printedmidsole that is specifically formed for the user on the foot facingsurface, especially in the height direction, to the contours of the footof the user, and may be enforced or softened in areas that arespecifically chosen for each specific user, in the form of a gait, forcetransferred from the foot, as well as a contour analysis of the footeither during walking, running or stationary positioning.

Thus, the present invention may also relate to a shoe having a 3Dprinted midsole, made of a 3D printed structure in accordance with theabove disclosure.

Another way of controlling the resistance of the 3D printed structure ishow one wall is connected to a second wall, as well as the form of thewall. If one wall is connected to another wall at an angle, i.e. thatthe planes of the walls intersect at an angle, the second wall mayprovide an increased resistance to the first wall and vice versa, as thewalls are angled towards each other and provide structural resistance toeach other, especially if one wall is connected to a second wall alongits entire height.

The 3D printed structure may be provided with a plurality of walls,where the plurality walls define a plurality of cells having a centralaxis that is substantially parallel to the walls and having a radiusfrom a wall to the central axis.

When pressure is applied to the walls and when the force applied to thewall exceeds a certain limit, the wall will deform, and as the bottomend (second end) of the wall is restricted inside the shoe by the footfacing surface of the outsole, the first end will move in a directiontowards the second end, and for this to happen, the wall will deform, bybuckling, expanding or other ways, in order to allow the first end tomove in a downwards direction. As the wall will deform, it may beadvantageous that the deform of the wall is unrestricted in at least onedirection, i.e. in the direction towards the central axis of the cell.Thus, the deformed wall is allowed to deform freely into the cell, sothat the radius between the wall and the cell is reduced in at least onearea. The form of the cell, e.g. the shape of the cell seen from aboveor the side, may also influence the deformation of the wall, as aconnected wall and the angle of the connection may increase or decreasethe resistance of the wall.

A single cell may be provided by a circular wall, that in multiplelayers provides a cylindrical wall, where the outer surface of the wallmay be connected to a second wall. Thus, the cell structure may be aplurality of cylindrical cells, connected to other cylindrical cells viathe walls. The circular wall may comprise the first wall, the secondwall and/or the third wall, where the first wall, second wall and/or thethird wall may be areas of the circular wall at different positionsalong the circular wall. Thus, the first wall may e.g. be positioned atangles 0-60 degrees, while the second wall may be positioned at 61-120degrees, the third wall may be positioned at 121-180 degrees.Alternatively, the first wall may e.g. be positioned at angles 0-120degrees, while the second wall may be positioned at 121-240 degrees, thethird wall may be positioned at 240-360 degrees. The circular wall mayhave a rotation that is 360 degrees, where the rotation is around acentral axis of the circular wall, where the central axis extendsthrough the centre of the circular wall

In one or more embodiments a 3D printed structure of an elastic materialhaving at least a first wall and a second wall, the 3D printed structurecomprising: at least a first layer having a first wall part and a secondwall part, where the first wall part comprises in the first layer atleast a primary structural layer, the second wall part in the firstlayer comprises a first flexible layer, at least a second layer havingat least the first wall part and a second wall part, where the firstwall part in the second layer comprises a second flexible layer, wherethe primary structural layer has a first rigidity, and the firstflexible layer have a second rigidity, where the first rigidity islarger than the second rigidity.

This means that the first layer of the 3D printed structure has adifferent structure than the second layer. The walls of the 3D printedstructure may extend along a first axis, while the second wall may bepositioned to a side of the first wall, i.e. in a direction that is at aright angle from the first axis. Within the meaning of the presentdisclosure the second axis may be orthogonal to the first axis. Thus, 3Dprinted structure may have a number of layers having a varying structurein at least two directions, where the structure of the first wall partand the second wall part, or any subsequent wall part, may be repeatedin a different part of the 3D printed structure. This may mean that thestructure of the first wall part and the second wall part may berepeated in a direction of the first axis and/or the direction of thesecond axis, in order to provide a plurality of walls and/or a pluralityof layers to provide a 3D structure having a specific rigidity, whichmay be a combination of structural layers and flexible layers in one ormore walls or wall parts of the 3D structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is an explanation of exemplary embodiments with referenceto the drawings, in which

FIGS. 1a and 1b show sectional view of a first and a second embodimentof a 3D printed wall in accordance with the description,

FIGS. 2a, 2b, and 2c shows a sectional view of a 3D printed wall, andhow the wall may react when a compressive force is applied.

FIG. 3 shows a perspective view of one example of a 3D printed wall

FIG. 4 shows a sectional view of a further embodiment of a 3D printedwall,

FIG. 5 shows a microscopic view of three sections of 3D printed walls,

FIGS. 6a, 6b and 6c shows three separate layers of a 3D printedstructure,

FIGS. 7a and 7b shows a perspective view of a layered structure indifferent steps, and

FIG. 8 shows a sectional view of a part of a 3D printed structure.

DETAILED DESCRIPTION

FIG. 1 shows a first exemplary embodiment of a 3D printed structure 1seen in a schematic sectional view, having a first wall 2 having aplurality of layers extending along a first axis A. The first wall 2comprises a primary structural layer 3, a first flexible layer 4 and asecond flexible layer 5. In this exemplary embodiment, the first wall 2comprises a secondary structural layer 6, a tertiary structural layer 7and a quaternary structural layer 8, where the secondary 6 and thetertiary 7 structural layers, as well as the tertiary 7 and quaternary 8structural layers each are separated by two flexible layers 9, 10, 11,12, respectively. I.e. where the structure of the primary structurallayer 3 and the first and 3 the second 4 flexible layers is repeatedalong the length of the wall 2 in the longitudinal direction A of thewall 2.

The primary structural wall 3 and the first 4 and second 5 flexiblewalls, as well as the subsequent walls, are 3D printed using an extrudedline of flexible material having a height H and a width W, and where onelayer of material in the 3D printed structure may be the height H, andmay be applied in a continuous manner as required in the 3D printedstructure.

In this embodiment, the structural layer 6 in this wall 2 are providedas two separate lines 12, 13 of extruded flexible material, where thetwo separate lines 13, 13′ are joined to each other at a joining sidewall, where the joining side wall 14 provides a permanent bond betweenthe two lines 13, 13′ of material. Furthermore, the structural layer 6may be joined to at least one flexible wall 5, 9 where an upper 15 or alower 16 wall of the flexible wall may be joined to an upper or lowerwall of the structural layer 6, creating a permanent bond between thetwo layers. The bond between the layers may extend along the entirelength of the layer 6, 5, 9 along an axis B which is substantiallyperpendicular to the 2D plane represented in the present sectional view.The flexible layers 9, 10 may also be bonded along the entire length ofthe layer 9, 10. As seen in this embodiment, the structural layer 6, hasa width that is approximately twice the width (2W) of the flexible layer5, 9 (W). The width of the structural layer 6, ensures that the layerhas a higher rigidity than the flexible layers 5, 9, so that when acompressive force is applied in the direction of the first axis A to thewall 2 the structural layer 6 will resist deformation for a longer timethan the flexible layer. The same considerations may be made for all thestructural and flexible layers shown in FIG. 1 a.

Similarly, FIG. 1b shows another exemplary embodiment of a wall 20,where the wall comprises a primary structural layer 21, a secondarystructural layer 22, as well as six flexible layers 23, 24, 25, 26, 27,28 that separate the primary structural layer 21 from the secondarystructural layer 22, in a direction of the first axis A. Two moreflexible layers are provided below the secondary structural layer 22. Inthis embodiment, the number of flexible layers is increased in view ofthe embodiment shown in FIG. 1a , which means that collective rigidityof the wall 20 is less than the wall 2 shown in FIG. 1a , assuming thatthe two walls are manufactured in a similar manner, of a similarmaterial and similar dimensions as the lines of flexible material havinga similar height (H) and width (W). The increase in flexibility is dueto the fact that the wall has more flexible layers per unit of lengthalong the axis A, than the wall 2 in FIG. 1a . Thus, when a compressiveforce is provided in the direction of axis A, the structural layers 21,22 will resist deformation while any one of the flexible layers 23, 24,25, 26, 27 may deform prior to the structural layers 21, 22.

FIG. 2a shows a wall 30 having three structural layers 31, 32, 33 thatare separated from each other by a first set of three flexible layers34, 35, 36 and a second set of flexible layers 37, 38, 39. When the wall30 is in its uncompressed state the first axis A intersects a centralpart of each layer, so that the wall 30 may have a substantiallystraight shape.

An increase in compression force in the direction of the axis A willcause a deformation of the flexible material of the layers 34, 35, 36,37, 38, 39 causing the shape of the wall 30 to change due to theflexibility of the material, and with an increase in compressive force,the wall 30 will eventually deform in such a way that the wall will bendaway from the first axis A. In the assumption that the first end 40 ofthe wall and the second end of the wall 41 are in a fixed in position,the deformation of the wall will most likely occur in a central part 42of the wall 30, where the central part 42 of the wall 30 will deflectaway from the first axis A. As the wall is made up of layers havingdifferent rigidity, it is highly likely that the parts of the wallhaving a lower rigidity, such as the flexible layers 34, 35, 36, 37, 3839 will be the first areas that will deform, and therefore cause thedeflection of the wall from the axis A in the areas of the flexiblelayer 34, 35, 36, 37, 38, 39 where the structural layers 31, 32, 33 willresist the deformation up to a certain point. One example of thedeformation may be seen in FIG. 2b , where two flexible layers 35, 38have deflected in a transverse direction C, where both layers havedeflected in the same direction c1, causing the length of the wall toreduce from its initial length X to its compressed length Y, as may beseen in FIG. 2 b.

In FIG. 2c , the same situation is shown, where a compression force hasto be applied to the wall 30, where the flexible layer 35 deflects inthe direction c1 and the flexible layer deflects in the direction c2.The directions c1 and c2 are only shown as examples, and the flexiblelayers can deflect in the same direction, opposite directions, oralternate directions. A similar deflection may occur when the number offlexible layers is only two, where the flexible layer may deflect in adirection away from the first axis A in a direction shown by the axis C.

FIG. 3 shows another embodiment of a 3D printed structure 1, seen in aschematic, having a schematic sectional view, having a wall 50, wherethe wall comprises at least a primary structural layer 51, and a firstflexible layer 52 and a second flexible layer 53. The wall furthercomprises a secondary structural layer 54, as well as four additionalflexible layers 55, 56, 57, 58. Each of the layers of the wall 50 has alongitudinal axis D, which extends along the centre of the layer alongthe length of each layer.

The 3D printed structure shown in FIG. 3, is formed so that thelongitudinal axis D of the layers 51-58, is substantially centered alongthe length of the wall 50 in the direction of axis A, i.e. that the axisD intersects the longitudinal axis D of each of the layers. This meansthat when a compression force is applied to the wall 50 in a directionof the axis A, the force translates to the centre of each layer, and mayassist the wall 50 in maintaining its height (X as shown in FIG. 2a ) upto a predefined magnitude of compression force, before the flexiblelayers begin to deform and defer away from the longitudinal axis A,similar to what is shown in FIGS. 2b and 2 c.

FIG. 4, shows a schematic sectional view of a wall 60, having threestructural layers 61, 62, 63 and six flexible layers 64, 65, 66, 67, 68,69, similar to what is shown in FIGS. 2a-2c . In this exemplaryembodiment, the longitudinal axis D of flexible layers 65 and 68 hasbeen offset in the direction c1 and c2 away from the longitudinal axisof the wall 60, where this offset of the longitudinal axis ensures thatwhen a compression force is applied in the direction of the longitudinalaxis A of the wall 60, the flexible layers 65 and 68 are predisposed orbiased to deflect in the directions c1 and c2, allowing the wall 60 tobend in these directions. The offset of the longitudinal axis of thelayers does not necessarily have to be in opposite directions, but maybe in the same direction. The offset may also be introduced into one ormore of the structural layers, in order to translate the compressiveforce in a diagonal direction (a product of direction A and direction c1or c2) to force a specific deformation of the wall.

FIG. 5 shows a microscopic view of a sectional cut of a 3D printedstructure, showing three examples of walls 70, 80 and 81, each having afirst end 71 and a second end 72, where each wall 70, 80, 81 has aplurality of flexible layers 73 and a plurality of structural layers 74,where the structural layers 74 are separated by flexible layers. As maybe seen in this figure, the layers of material bond with each other,creating a somewhat uniform structure from the first end 71 to thesecond end 72, where each layer 73, 74 are fused to each other. Here itis clear that the structural layer has a larger width (2W) than theflexible layers (W), which increases the rigidity of the structurallayers 74 is higher than the rigidity of the flexible layer 73.

FIGS. 6a-6c show separate layers of a 3D printed structure, where FIG.6a shows a first layer 90, FIG. 6b shows a second layer 91 and FIG. 6cshows a third layer 92. When the 3D printed structure is beingconstructed via 3D printing, where the first layer 90 may be seen as abase layer, the second layer 91 may be positioned on top of the firstlayer 90, and the third layer 92 may be positioned on top of the secondlayer 91. If a fourth layer is to be added to the 3D printed structure,the fourth layer may e.g. have the same structure as the first layer.

As may be seen in FIGS. 6a-6c , each layer is has a continuous line 94that follows a zig-zag pattern from the right side 95 to the left side96 of the layer 90, 91, 92. The construction may be formed in such a waythat the line creates a plurality of hexagons 97, where each hexagon hassix walls 98. Two of the adjacent hexagons 97 a, 97 b to one hexagon areprinted in such a manner that there are two walls 98 a, 98 a′ thatseparate the hexagons 97 a and 97 b, while, while four of the adjacenthexagons 97 c (only two of these have reference numbers) have a singlewall separating from the first hexagon 97. Thus, the two walls in asingle layer create a structural layer, as the two walls 98 a, 98 a′bond with each other and have a higher rigidity than the single wall.Thus, the hexagons that are only separated by a single wall 98 b, 98 c,98 e, 98 f, create a flexible wall.

The next layer, i.e. the second layer 91, as shown in FIG. 6b , is thenproduced, in such a way that the structure of the layer 91 is rotated by60 degrees, relative to the first layer 90, which means that the twowalls, which were present on two walls of the hexagon, now lie on top ofa flexible wall (98 b, 98 e of FIG. 6a ), so that the structural layerof the second layer 91 now abuts a flexible layer in the longitudinaldirection of the wall (axis A in FIG. 1).

The next layer, i.e. the third layer 92, as shown in FIG. 6c , is thenproduced, in such a way that the structure of the layer 92 is rotated by60 degrees (a), relative to the second layer 90 (120 degrees rotationrelative to the first layer 90), which means that the two walls 98 a, 98a′, which were present on two walls of the hexagon, now lie on top of aflexible wall (98 c-98 e of FIG. 6a ), so that the structural layer ofthe second layer 91 now abuts a flexible layer in the longitudinaldirection of the wall (axis A in FIG. 1).

Thus, by adding layers on top of each other and rotating the layers acertain degree, it is possible to construct a hexagonal cell, where thewalls of the hexagonal shape have a structure as shown in e.g. FIG. 1a ,where the wall has a primary structural layer, and a first and a secondflexible layers in the direction of the axis A. The axis A may be seenas an axis that is a normal to the two dimensional plane shown in FIG.6a-6c , where the longitudinal axis of the wall rises up from the planeof the drawings towards the reader.

FIGS. 7a and 7b show a perspective view of the process disclosed in FIG.6a-6c , where the leftmost structure shows a first layer 100 of 3Dprinted structure, where the double wall 101 has a first angle, and hastwo neighbouring single walls 103. In the second structure from theleft, a second layer 102 has been positioned on top of the first layer101, where the double wall 101 now abuts a single wall 103 by rotatingthe structure of the layer 60 degrees, and where a single wall 103 nowis positioned on top of the double wall in the first layer. The thirdstructure from the left shows where a third layer 104 has beenpositioned on top of the second layer 102, where the double wall now ispositioned on top of a single wall 103 of the second layer 102, and asingle wall 103 of the third layer has been positioned on top of thedouble layer 101 of the second layer. The fourth structure from the leftnow shows how a fourth layer 105 having a structure that is somewhatidentical to the first layer is positioned on top of the third layer, sothat a double wall 101 is positioned on top of a single wall 103, and asingle wall 103 of the fourth layer is positioned on top of a doublewall 101 in the third layer.

By the provision of the layers on top of each other in the manner asshown in FIG. 1 by rotating the double wall in each height, it ispossible to construct a wall as shown in FIG. 1-FIG. 5, where astructural layer (double wall) is followed by a flexible layer (singlewall). The rotation may be done in a different manner, where each layermay be provided in different rotation and structure, so that the desiredstructure of a wall may be obtained. Furthermore, the rotation of thelayers may be done differently, when the cells have a different shape,i.e. for a triangular shape of a cell, the rotation may be a product ofabout 120 degrees, for a rectangular shape, the rotation may be e.g. aproduct of 90 degrees, to obtain a certain structure. If the shape ofthe cells is circular, any angle may be utilized for rotation, to obtaina structure. Thus, the rotation of the layers may be adjusted in view ofthe shape of the cells or the walled structure of the 3D printedstructure.

FIG. 8 shows a schematic cross-sectional view of a structure of a cell200, showing three adjacent walls 201, 202, 203, that are attached toeach other in the direction C. Each wall has a structural layer 204,followed by two flexible layers 205, 206, in a repeating pattern in thedirection of the axis A. In other embodiments, any of the walls shown inthe previous embodiments may be utilized, in order to obtain a certainpattern, structure of walls, as well as adjacent walls. In oneembodiment, the pattern of adjacent walls may be any suitable pattern,where e.g. the pattern of structural and flexible layers shown in inFIG. 1a , may be provided in one wall, where the adjacent wall may havea pattern as e.g. shown in FIGS. 1b, 1c , or FIG. 4. Thus, there is norequirement of a specific pattern of walls, and this pattern can beadjusted for a specific application, where one wall has a first rigidityfollowed by another wall having another flexibility, that may be higheror lower than the first wall.

When viewing the 3D printed structure in FIG. 8 in the direction of axisC, it is possible to see that each layer of material of the structurehas, having a second axis E, has at least one structural layer 204 and afirst 205 and a second flexible layer 206. Thus, the 3D printedstructure may in one layer may define a layer of a wall, where one ofthe walls may have a structural layer having a higher rigidity while thetwo adjacent walls may have, or on each side of the structural wall, mayhave a flexible wall.

Furthermore, when viewing the structure of FIG. 8, it is also possibleto see that the structure of the structural walls may be seen as havinga diagonal pattern, along the axis F, as shown in FIG. 8. When moving ina direction C it may be seen that the structural layer is replaced by aflexible layer 205, and the next structural layer 204 to the side, i.e.in the adjacent wall 202 is one layer lower than the first structurallayer 204 of the first wall 201. The same may be stated in view of thethird wall 203 in the structural layer 204 is one layer lower than theprevious structural layer 204 in the second wall 202. Thus, seen inthree dimensions, the structural layers 204 follow a helical axis, wherean adjacent wall has a structural layer a layer lower than the previouswall.

In this embodiment a structural layer 204 abuts a flexible layer in thedirection of axis A, and may also abut a flexible layer in the directionof axis E. Thus, a structural layer 204 in the first layer 207 of the 3Dprinted structure 200 may have a flexible layer 205 that abuts thestructural layer 204 in the second layer 208 of the 3D printed structure200. Furthermore, the second wall 202 may be provided with a flexiblelayer 205, which abuts the structural layer 204 in the first layer 208.Yet further, the third wall 203 may further be provided with a flexiblelayer 205, which abuts the flexible layer 205 in the first layer 208 inthe direction of the axis E.

The third layer 209 may yet further be provided with a flexible layer205 or a structural layer 204 in the direction of axis A, abutting aflexible 205 or a structural layer 204 in the previous layer 208.

The walls of the embodiment shown in FIG. 8 may be seen as having athird axis F, where the third axis may be seen as following the walls ofthe cells (as seen in FIGS. 7a and 7b in a helical manner. Thus, thehelical axis F may extend diagonally downwards, where the axis Fintersects a structural layer 204, in each wall. The view shown in FIG.8 is distorted, as the view is seen from the side in two dimensions. Thehelical axis may be seen as a curve in three-dimensional space and maybe similar in shape to a coiled spring, or similar to a handrail in aspiral staircase, where the helical axis moves downwards in a “screwing”motion, in the shape of e.g. a cylindrical helix.

In accordance with the present disclosure, the exemplary embodiments ofone, two or three walls of the 3D printed structure is to be understoodas being combinable. I.e. in a figure showing one wall, the same wallmay be utilized as a second, third or any subsequent wall or wall partin accordance with the description. The person skilled in the art willnot have any problem in combining disclosures of one embodiment withanother embodiment based on the present description of the 3D printedstructure.

The use of the terms “first”, “second”, “third” and “fourth”, “primary”,“secondary”, “tertiary” etc. does not imply any particular order, butare included to identify individual elements. Moreover, the use of theterms “first”, “second”, “third” and “fourth”, “primary”, “secondary”,“tertiary” etc. does not denote any order or importance, but rather theterms “first”, “second”, “third” and “fourth”, “primary”, “secondary”,“tertiary” etc. are used to distinguish one element from another. Notethat the words “first”, “second”, “third” and “fourth”, “primary”,“secondary”, “tertiary” etc. are used here and elsewhere for labellingpurposes only and are not intended to denote any specific spatial ortemporal ordering.

Furthermore, the labelling of a first element does not imply thepresence of a second element and vice versa.

Although features have been shown and described, it will be understoodthat they are not intended to limit the claimed invention, and it willbe made obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe claimed invention. The specification and drawings are, accordinglyto be regarded in an illustrative rather than restrictive sense. Theclaimed invention is intended to cover all alternatives, modifications,and equivalents.

1. A 3D printed structure of an elastic material, the 3D printed structure having at least a first layer and a second layer, the 3D printed structure comprising: at least a first wall configured to deform when a first force is applied to the first wall in a direction of a first axis and configured to return to an original form of the first wall when the applied first force is released, the first wall comprising at least a primary structural layer and at least a first flexible layer; and at least a second wall configured to deform when a second force is applied to the second wall in a direction of a second axis and configured to return to an original form of the second wall when the applied second force is released, the second wall comprising at least a secondary structural layer and at least a second flexible layer, wherein a third axis of the 3D printed structure intersects the first layer of the 3D printed structure and the second layer of the 3D printed structure and wherein a third axis intersects the primary structural layer and the secondary structural layer, and wherein the primary structural layer has a first rigidity and the first flexible layer has a second rigidity, wherein the first rigidity is greater than the second rigidity.
 2. A 3D printed structure according to claim 1, wherein the 3D printed structure comprises a third layer and at least a third wall comprising at least a tertiary structural layer and at least a third flexible layer, wherein the third axis intersects the third layer of the 3D printed structure and the tertiary structural layer.
 3. A 3D printed structure according to claim 2, wherein the first wall, the second wall, and the third wall are arranged along parallel axes.
 4. A 3D printed structure according to claim 1, wherein the primary structural layer and the secondary structural layer are positioned in different layers in the 3D printed structure.
 5. A 3D printed structure according to claim 2, wherein the tertiary structural layer is positioned in a different layer of the 3D printed structure than the primary structural layer and the secondary structural layer.
 6. A 3D printed structure according to claim 1, wherein the first wall abuts the second wall.
 7. A 3D printed structure according to claim 1, wherein the first wall and the second wall form part of a closed cell defining a predefined volume of the cell.
 8. A 3D printed structure according to claim 1, wherein the third axis of the 3D printed structure is at least one of a helical axis or a spiral axis.
 9. A 3D printed structure according to claim 1, wherein the primary structural layer is part of the first layer of the 3D printed structure and the secondary structural layer is part of the second layer of the 3D printed structure.
 10. A 3D printed structure according to claim 1, wherein the intersection of the third axis with the primary structural layer is in the same position as the intersection of the third axis with the first layer of the 3D printed structure, and wherein the intersection of the third axis with the secondary structural layer is in the same position as the intersection of the third axis with the second layer of the 3D printed structure.
 11. A 3D printed structure according to claim 2, wherein the intersection of the third axis with the tertiary structural layer is in the same position as the intersection of the third axis with the third layer of the 3D printed structure.
 12. A 3D printed structure according to claim 1, wherein the elastic material is a silicone material or a mixture of a silicone material.
 13. A 3D printed structure according to claim 1, wherein the primary structural layer is made from a first material composition and the first flexible layer is made from a second material composition, wherein the first material composition is different from the second material composition.
 14. A 3D printed structure according to claim 1, wherein the primary structural layer and the first flexible layer are configured to have the first rigidity and second rigidity, respectively, along at least one of a longitudinal direction, a transverse direction, or a rotational direction.
 15. A 3D printed structure according to claim 2, wherein the third wall abuts the second wall.
 16. A 3D printed structure according to claim 1, wherein the secondary structural layer is made from a first material composition and the second flexible layer is made from a second material composition, wherein the first material composition is different from the second material composition. 